Yes, I had a shell case rupture similar to your experience. It was however Winschester factory ammo (white box). Didn't bust the bolt or extractor like you but blew a steel GI mag apart blowing the base out, and covering my face in black soot.
The weapon (M16A2) was fine. I think I still have that shell somewhere in my collection of weird things.
My shell was a lot cleaner looking than yours (probably better powder) with an obvious crack from the primer pocket outward and about an 1/8" up the side of the case.
If you really want experience a true WTF moment though...experience a ruptured .50-cal while firing an M2.
Brass is brass a metal and there is always a chance new or reloaded that there is a weak spot where it matters most - around or near the primer or extractor lip.
One in a million!